WATER MANEGEMENT BY GREY WATER TREATMENT

Transcription

1 WATER MANEGEMENT BY GREY WATER TREATMENT 1 PROF. U. R. DESAI, 2 PROF. S. B. JOSHI, 3 PROF. N. M. JOSHIPURA 1 Asst.Pressor, Department Of Civil Engineering, B. H. Gardi College Of Engineering And Technology, Anandpar, Rajkot 2 Pressor And Head Department, Department Of Civil Engineering, G. K. Bharad College Of Engineering And Technology, Tramba, Rajkot 3 Asst.Pressor, Department Of Civil Engineering, L. E. College, Morvi mehtau2003@yahoo.co.in, sbjoshi29960@yahoo.co.in, nehajoshipura@rediffmail.com ABSTRACT: Management and conservation urban water has become a serious development issue in many developing countries. Population and water need rise rapidly, whereas, water availability is decreasing due to inefficient management and deterioration. If the problem is not given a serious look, then the future generations may have to face severe crisis water. The aim this study is towards the management water by Greywater recycling for proposed area Rajkot. In this present study design various components grey water treatment is suggest for proposed area. various components for Grey Water treatment has been suggested for proposed area under study. Costs all the components are also determined in this study. Total cost Grey water treatment is Rs Keywords Water Management, Grey Water, Components grey water treatment I: INTRODUCTION Water management is the activity planning, developing, distributing and managing the optimum use water resources. In an ideal world, water management planning has regard to all the competing demands for water and seeks to allocate water on an equitable basis to satisfy all uses and demands. [1] Historically water has always been a key factor in deciding where a town is established with most cities and towns usually located within close proximity to a reliable water source. Water has subsequently been used at an increasing rate in these cities and towns for both consumption and industry over time. Rising populations and rapidly changing climatic conditions are putting a strain on water resources across the globe as a consequence continued and increasing demand for potable water. [2] Fig.1Availability fresh water Source: A report prepared by Green Energy Foundation, 2010 Water should be viewed as a finite resource that needs to be recycled and reused in order to preserve it. Only 2.5% the world s water is fresh, while 97.5% is ocean. And that freshwater, only 0.3% is available from rivers, lakes and reservoirs. Most freshwater is locked up in polar ice, glaciers or soil moisture. Unfortunately, more and more that precious freshwater is contaminated each year. [3] In many part the Globe, population growth and urbanization are increasingly becoming challenges to Governments. According to the information from the International Year Freshwater (2003), by the year 2020, some 60% the global population will live in urban areas. Currently, more than 80 countries, with 40% the global population suffer from severe water shortages. In the developing countries Asia urban water supplies have progressed little in the last 20 years. [4] II: GERY WATER According to the levels cleanliness, the water we use can be classified into three types namely white water, black water and grey water. White water is fresh, completely clean and potable. Black water is used water which is heavily polluted by chemicals and/or biological contaminants. It is basically nonuseable sewage water. Grey water is in between the two in terms sanitation. This includes water from showers, bathtubs, sinks, kitchen, dishwashers, laundry tubs, and washing machines. It commonly contains soap, shampoo, tooth paste, food scraps, cooking oils, detergents and hair. Greywater makes up the largest proportion the total wastewater from households in terms volume. Typically, 50-80% the household wastewater is greywater. ISSN: NOV 12 TO OCT 13 Volume 2, Issue 2 Page 111

2 Greywater is less polluted wastewater which represents 60 to 70 % the domestic water use. Over 50% the water demand for domestic activities can be met by treated greywater than fully treated water; including applications such as toilet flushing, gardening and car washing etc. Greywater recycling & reuse is an effective and economical way solving water scarcity. [5] III: WHY GREYWATER RECYCLING? The main purpose greywater recycling is to substitute the precious drinking water in applications which do not require drinking water quality. Nonpotable reuse applications include industrial, irrigation, toilet flushing and laundry washing dependent on the technologies utilised in the treatment process. With greywater recycling, it is possible to reduce the amounts fresh water consumption as well as wastewater production, in addition to reducing the water bills. If greywater is regarded as an additional water source, an increased supply for irrigation water can be ensured which will in turn lead to an increase in agricultural productivity. Unlike rainwater harvesting, greywater recycling is not dependent on season or variability rainfall and as such is a continuous and a reliable water resource. This results in smaller storage facilities than those needed for rainwater harvesting. Greywater has a relatively low nutrient and pathogenic content and therefore, it can be easily treated. Moreover, if space is not available, it can be installed in the cellar. [5] Greywater systems have been in the market for several years but are yet to be fully accepted by the general public. The systems provide a good water conservation tool as they reduce the use potable water. There may be widespread confusion within the general public as to what exactly greywater comprises, given the lack a uniform definition within the literature. Clarity is necessary for the promotion grey water systems as safe water conservation technologies. Grey water reuse has been a long practice in country and areas with limited water resources, with application predominantly for water gardens and lawn in the USA and for landscaping, fountains and toilet flushing in Japan. IV: ESTIMATION OF GREY WATER PER PERSON Grey water makes up approximately 50 to 80 percent all wastewater coming from homes and other residences. As per WHO, water required for bathing, washing clothes, washing utensils and other is about 90 lpcd. GREY WATER COLLECTION FROM ONE COLONY IN RAJKOT CITY The colony named. Savan Sapphire lies in Rajkot having 3 towers four floors and having four flat in each floor. So, total numbers flats are 48. Total nos. flats = 48 No. persons in each flat = 4 Total no. persons = 200 Grey water from each person = 90 lpcd Total grey water generated = 90 x 200 x 0.9 = lpcd = 17 KLD VI: GREY WATER TREATMENT There are multiple variations greywater system design, but most treatment systems consist six major components: (1) Screening (2) Equalization tank (3) Sedimentation (4) (5) Filtration water (6) Disinfection water DESIGN OF BAR SCREEN The function the bar screen is to prevent entry solid particles/ articles above a certain size; such as plastic cups, paper dishes, polythene bags etc into the Grey water treatment plant. (If these items are allowed to enter the Grey water treatment plant, they clog and damage the pumps, and cause stoppage the plant.) Table: 1 Assumption in Bar Screen Sr. Parameter Units No. 1 Size bar 10mm x 50 mm 2 Spacing between 10 mm bars 3 Angle inclination 45 4 Velocity through the 0.6 m/s screen 5 Approach velocity 0.3 m/s 6 Depth incoming screen 0.07 m Table: 2 Bar Screen Average Daily 17 KLD Quantity grey water Peak hourly velocity Cross section area the screen channel Adjust for the area blocked by the bar. = 3 x Avg. hourly = 3 x 1.97 x 10-4 m3/sec = x 10-4 m3/sec 0.30 m/sec x 10-4 / 0.3 = 1.97 x 10-3 m2 = 1.97 x 10-3 m2 x 1.5 = 2.95 x 10-3 m2 The peak is assumed to be three times the average Volume/Hr = Cross-sectional area x velocity Cross-sectional area is increased by 50% to compensate for the obstruction posed by the bars the grill. ISSN: NOV 12 TO OCT 13 Volume 2, Issue 2 Page 112

3 Numbers opening Numbers bars Width the screen Length the screen Velocity in screen Head loss x 10-3 /(0.07 x 10/1000) = 5 4 = (5 x 10/1000)+ (4 x 10/1000) = 0.09 m =0.52 m L= (d+ 0.03) cot θ (W + ds) 0.03 m/sec = Q/W x d m DESIGN OF OIL AND GREASE TRAP The grease and grit trap is placed at the discharge point the canteen/ kitchen area itself to arrest solid and fatty matter at source. The wastewater output from this unit is taken to the equalization tank. Table: 3 Oil and Grease Trap Total quantity 17 KLD Quantity Hourly average sewage in =17 m3/day = 17/24 m3/hr = m3/hr volume = x 30/60 m3 = m3 Water depth in tank area grey water is designed to hold resident time 30 min. average. 0.6 m = 0.354/0.6 m2 = 0.59 m2 DESIGN OF EQUALIZATION TANK Flow equalization simply is the damping rate variation to achieve a constant or nearly constant rate and can be applied in number different situation; depending on the characteristics collection system. The sewage from the bar screen chamber and oil, grease and grit trap comes to the equalization tank. The equalization tank is the first collection tank in Grey water treatment. Its main function is to act as buffer: To collect the incoming raw sewage that comes at widely fluctuating rates, and pass it on to the rest the STP at a steady (average) rate. The equalization tank must be sufficient capacity to hold the peak time in volumes. Table: 4. Equalization Total 17 KLD Quantity quantity =17 m3/day grey water Hourly = 17/24 m3/hr average sewage in Equalization tank volume = m3/hr = x16 m3 = m3 Free board 0.3 to 0.5 ma in Water depth in tank area Diffuser Air quantity required 2.0 to 2.5 m = 11.33/2 m2 =5.67 m2 L = 2.5m B = 2.5 m Select size and number to suit the dimensions the tank 0.8 x = 9.06 m3/hr Typically, a pair diffusers must fit within the width the tank. If the tank is not wide enough, the pair may be placed at an angle. Several such pairs diffusers are placed along the length the tank. Air provided at rate 0.8 m3/m3 hr PRIMARY SEDIMENTATION TANK Clarification, through the process sedimentation is the separation suspended particles by gravitational settling. This operation can be used for grit and solids removal in the primary settling basin, removal oil and grease, removal chemically treated solids when the chemical coagulation process is used or solids concentration in sludge thickeners. Efficiently designed and operated primary sedimentation tank should remove from 50 to 70 percent the suspended solid and from 25 to 40 percent the BOD. Table: 5 Assumptions in the Sedimentation Sr. Parameters Values No. 1 Over rate 1 m3/m2.hr 2 Flow rate 17 KLD 3 Detention time 2.5 hr Table: 6 Sedimentation Flow rate 17 KLD ISSN: NOV 12 TO OCT 13 Volume 2, Issue 2 Page 113

4 Water depth in tank area =17 m3/day = 17/24 = M3/Hr 2.5 m = 0.708/1 m2 = m2 L = 1m B = 1 m DESIGN OF AERATION TANK The tank (together with the settling tank/ clarifier that follows) is at the heart the treatment system. The bulk the treatment is provided here, employing microbes/bacteria for the process. The main function the tank is to maintain a high population level microbes. This mixture is called MLSS (Mixed Liquor Suspended Solids). Table: 7 Grey water quality BOD in grey water BOD Load/Day 17 KLDBOD in sew 300 mg/l = kg/l = (17 x 1000) x = 5.1 kg/day F/M ratio 0.12 M (Biomass M (biomass) MSLL level Volume = 5.1 / 0.12 = 42.5 kg 3500 mg/l (= 3.5 kg/ m3) = 42.5 / 3.5 = m3 Average retention time Quantity Grey water This means the aeration tank has to supply 30 kg Oxygen every day. (This is the Food in the F/M ratio.) The acceptable MLSS range is But we chose the lowest MLSS in the range in the range, because it gives us the most conservative size for the aeration tank (see the row below). = Biomass / MLSS Selecting lowest MLSS yields the highestpossible size Retention Time Depth Area width Length BOD Load/hour Air for BOD Air for mixing Air for mixing Air to be supplied Select size diffuser No diffuser Placement diffusers = 12.14/ 17 x 24 Hrs = Hrs 3.0 m = 12.14/3 = 4.04 m2 for the aeration tank. This size will be able to handle higher values MLSS. Area = Volume / Depth 3.5 m This width is ideal to accommodate set 1m long Diffusers = 4.04/3.5 Length = = 1.16 m Area/width =5.1/22 = 0.23 Kg/day = 0.23x60 = 13.9 m3/hr = 13.9x1.1 = 15.3 m3/hr. = 2 x 4.04 = 8.08 m3/hr = (BOD load per day) / (no. aeration hours). Assuming 22 hrs aeration. This m3/m3 tank Volume This 2 m3/hr / m2 floor area 15.3 m3/hr The highest quantity the three iterations above. 90 OD x 1000 Length OD-outer dia. = 15.3 /8 = 2 Nos. (nearest PRESSURE FILTER whole number) 2 diffusers (1 pairs) Rows are distributed evenly along the length the tank. ISSN: NOV 12 TO OCT 13 Volume 2, Issue 2 Page 114

5 The pressure sand filter (PSF) is used as a tertiary treatment unit to trap the trace amounts solids which escape the clarifier, and can typically handle up to 50 mg/l solids in an economical manner. This unit is essentially a pressure vessel that is filled with graded media (sand and gravel). The water filtered with PSF is passed on to the next stage in the STP chain: the Activated Carbon Filter. Table: 8 Pressure Filter throughput filtration hour Filtration Rate Loading rate on filter Filter cross section area required(min) Diameter filter(min) 17 m3/day Quantity grey water. 20 Hrs (per day) Allow 4 hours for rest, backwash, etc. = 17 / 20 The filter = 0.85 m3/hr must be able Loading rate on to handle the clarified water at this rate. 12 m3/m2 / Hr Filter crosssectional = 0.85 / 12 = m2 = (0.071 x 4/ π)1/2 = 0.3 m = (Filtration rate) / (Loading rate) Area a circle= π/4 x Dia2 Height m Selected by filter convention Depth sand layer m Selected by convention ACTIVATED CARBON FILTER An activated carbon filter, like the Pressure Sand Filter, is a tertiary treatment unit. It receives the water that is already filtered by the Pressure Sand Filter and improves multiple quality parameters the water: BOD, COD, clarity (turbidity), colour and odour. 4.9 Activated Carbon Filter throughput filtration hour 17 m3/day 20 Hrs (per day) Filtration Rate = 17 / 20 = 0.85 m3/hr Loading rate on The filter must be able to handle the clarified water at this rate. Loading rate on filter Filter cross section area required(min) Diameter filter(min) 10 m3/m2 / Hronal = 0.85 / 10 = m2 = (0.085 x 4/ π)1/2 = 0.33 m = (Filtration rate) / (Loading rate) Area a circle= π/4 x Dia2 Height m filter Depth sand m layer SODIUM HYPO DOSING SYSTEM The filter should be able to treat all the water that is decanted from the Secondary Clarifier tank Sodium HYPO Dosing System throughput 17 m3/day Dose on daily basis max. chlorine dose Chlorine dose per day Hypo dose per day Select hypo tank capacity 5 PPM = 5 mg/l = kg/m3 = 17 x = kg = / 0.1 = 0.85 kg/day 50 L Hypo is available at 10 % strength. Dose pump 0-4 L/Hr rating COST OF ALL COMPONENTS IN GREY WATER TREATMENT Sr. No. Unit Size Cost 1 Bar screen 0.6m x 0.09m x 0.07m 2 Oil & Grease 1m x 1m x trap 0.6m 3 Equalization 2.5m x 2.5m x 3m 4 1.5m x 3.5m x 2.5m 5 Sedimentation 1m x 1m x 2.5m 6 Pressure Sand Dia. 0.3 m, Filter ht. 1.5m 7 Activated Dia. 0.3 m, Carbon Filter ht. 1.5m 8 Storage 3m x 2.5m x 2.5m 9 Other mechanical ISSN: NOV 12 TO OCT 13 Volume 2, Issue 2 Page 115

6 units Total cost VI: CONCLUSION Greywater makes up the largest proportion the total wastewater from households in terms volume. Typically, 50-80% the household wastewater is greywater. various components for Grey Water treatment has been suggested for proposed area under study. Costs all the components are also determined in this study. Total cost Grey water treatment is Rs The population growth the Rajkot city is very fast. In summer people suffer from water scarcity. They purchase water from private water suppliers. By Grey water recycling we can save large amount water. If people Rajkot focus on this study, they can get more water for domestic and Industrial purpose. Water problems Rajkot are solved by some extent. REFRENCES [1]Desmond Dinama, PG Thesis, Greywater Systems: Barriers for Builders School Property, Construction & Project Management. RMIT, August [2008]. [2]Green Energy Foundation, Report, Harvesting Rain water to meet the water shortage in Pune, [2010]. [3]Gopal K. sarangi, Towards a Public Private Partnership Regime: An Analysis Water supply in Urban India ASIEN 117, 2010, S [4] [5] Grey water recycling introduction, Report by fbr, Association for Rainwater Harvesting and Water Utilisation. [6]Grey water recycling introduction, Report by fbr, Association for Rainwater Harvesting and Water Utilisation. [7]Rajkot Municipal Corporation, Detail Project Report, Chapter 2, [2005]. [8] Orianna Courtency, Eklund Linda Tegelberg, PG Thesis, Small scale systems for Grey water reuse and disposal, Swedish University Agricultural Sciences, [2010]. [9]Manual Sewerage and Sewage Treatment, Central Public Health and Environment Engineering Organisation, Government India, Second Edition. ISSN: NOV 12 TO OCT 13 Volume 2, Issue 2 Page 116